Hi Ampers,
Well... during a weak moment I was overcome by temptation and purchased that
used QRO HF-2500DX I was looking at in late December.
I want to thank everyone for their feedback regarding what to look for in high
powered amp in general, to specific issues revealed in several earlier QRO
models, and specific information regarding the HF-2500DX product itself.
Here's my initial observations prior to feeding any RF into this monster. I
call it a monster because you don't want to be lugging this unit around solo,
unless you're extremely buff. And even so, I think a couple hundred feet might
be the upper limit at that! This amplifier is HEAVY. But keep in mind, a true
green-key RTTY fanatic like me LIKES heavy! (We don't need no stinkin' plastic
keyboards.)
Okay, so there's TWO hefty transformers in the cabinet. The larger one is a
pretty typical looking HV chunk of steel. The second one is a smaller chunk of
steel. The only criticism I can make is the lack of a rope/wire type handle on
the HV transformer. This would make it easier to remove and reinstall in the
cabinet.
Quality can be subjective. I separate my quality into at least two parts.
Components and workmanship.
Components: There is no question this amplifier uses high quality parts. All
fasteners are stainless steel, wiring is substantial gauge, Teflon material is
used as necessary, and the wiring is securely fastened. I already told you
about the heavy duty transformers. So I don't recognize anything being "cheap"
or "low quality" in here. The stainless hardware is nice, but is also a
catch-22. If you're prone to dropping a nut, washer, or screw, don't bother
reaching for your magnetic screwdriver. It's useless for fishing hardware out
of a corner!
Workmanship: High quality workmanship was used in the layout and construction
of this unit. I verified the two panel meters were indeed mounted using a RTV
type clear adhesive. This technique was new to me, but the meters are secure
and the craftsmanship is good. Whoever mounts those meters has perfected the
technique. One quality issue I did see was the lack of "de-fluxing" solder
rosin from circuit boards and connections. Other high-end amplifiers I have
owned have always been rosin free.
My next comments are made without knowing the repair history or the previous
owner(s) involvement in any modifications to this unit.
One goal for my new amplifier was a quiet cooling system. Some of the feedback
led me to believe this unit was going to be pretty loud. A suggestion to use
noise cancelling headphones helped elevate my apprehension. Here's the reality:
This HF-2500DX has a 2-speed fan which sounds very quiet to me. (Huh? What's
that you say?) Possibly a more quiet fan was retrofitted in this unit. I don't
know. I just discovered a fellow contester has a pair of these amplifiers so I
will have a better idea after visiting his shack.
Prior to my purchase decision, I opened the cabinet of the amplifier and went
inside "looking for trouble". I didn't find anything significant. There were no
toasted bandswitch contacts, no toasted resistors, and no carbonized flashover
points. The worse defect I discovered were 4 or 5 small solder splashes
floating around on the surface of the chassis. Whether these were left behind
from the manufacturing process or during a homebrew repair session, I couldn't
tell.
I am in the process of wiring and framing my new radio room so I haven't had
this amplifier on the air yet. I will follow up with a report of on-the-air
operation later. I will again be "looking for trouble" especially on 160 meters
and 10/12 meters, typically the toughest bands in an all-band HF amplifier.
IF YOU GOT THIS FAR...
I am looking for a pair of commercial plate cap connectors for the 4cx800
tubes. I am used to the finned heat sink type used in my Kenwood TL-922A
(3-500's). Does anyone know of a source for solid fittings?
73 de Bob - K0RC
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